Control system for plasma chamber having controllable valve

ABSTRACT

A control system for a plasma treatment apparatus includes a wafer treatment device. The wafer treatment device includes a vapor chamber and an upper electrode assembly. The upper electrode assembly includes a gas distribution plate having a plurality of holes. The upper electrode assembly includes an upper electrode having at least one gas nozzle and at least one controllable valve connected to the at least one gas nozzle for controlling a flow of gas from a gas supply to the holes via the at least one gas nozzle. The at least one gas nozzle is separated from the gate distribution plate by a gap. The control system includes a measurement device configured to measure a thickness profile of a wafer. The control system includes a controller configured to generate a control signal. The at least one controllable valve is configured to be adjusted based on the control signal.

PRIORITY CLAIM

The present application is a divisional of U.S. application Ser. No.15/822,469, filed Nov. 27, 2017, which is a divisional of U.S.application Ser. No. 13/486,374, filed Jun. 1, 2012, now U.S. Pat. No.9,840,778, issued Dec. 12, 2017, which are incorporated herein byreference in their entireties.

BACKGROUND

Electronic devices, such as integrated circuits and flat panel displays,are commonly fabricated by a series of process steps in which layers aredeposited on a substrate and the deposited layers are etched intodesired patterns. In some instances, the process steps include plasmaenhanced chemical vapor deposition (PECVD) processes. The trend inmicroelectronic circuits toward ever increasing densities and smallerfeature sizes continues to make plasma processing of such devices moredifficult. For example, in single wafer systems, pressure differencesand differences in treatment gas concentration leads to non-uniformitiesacross a surface of a wafer substrate, from a center of the wafersubstrate to an edge of the wafer substrate. The non-uniformities becomemore pronounced as a diameter of the wafer substrate increases. Suchnon-uniformities cause a variety of problems. For example, in themanufacture of semiconductors and integrated circuits, suchnon-uniformities often result in devices that either do not function orfunction in a decreased capacity.

Previous techniques utilized different gas distribution plates or focusrings for substrates having different diameters in order to compensatefor non-uniformities of the treatment gas. Identifying and installingthe correct gas distribution plate or focus ring is time consuming andcostly. In addition, the appropriate gas distribution plate for aparticular process is often not suitable for a different process.Consequently, in order to use the same chamber for different processes,the gas distribution plate is replaced which decreases an amount of timethe chamber is operating, thereby reducing a production yield. Inaddition, in gas distribution plates which provide concentric control oftreatment gas flow, the non-uniformity of the wafer surface isincreased.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments are illustrated by way of example, and not bylimitation, in the figures of the accompanying drawings, whereinelements having the same reference numeral designations represent likeelements throughout. It is emphasized that, in accordance with standardpractice in the industry various features may not be drawn to scale andare used for illustration purposes only. In fact, the dimensions of thevarious features in the drawings may be arbitrarily increased or reducedfor clarity of discussion.

FIG. 1 is a cross-sectional view of a plasma treatment apparatus inaccordance with at least one embodiment.

FIG. 2 is an exploded perspective view of an upper electrode assembly inaccordance with at least one embodiment.

FIG. 3 is a cross sectional view of the upper electrode assembly inaccordance with at least one embodiment.

FIGS. 4A-D are bottom views of various gas distribution plates for theupper electrode assembly in accordance with at least one embodiment.

FIG. 5 is a block diagram of a feedback control system in accordancewith at least one embodiment.

FIG. 6 is a schematic diagram of a controller of the plasma treatmentapparatus in accordance with at least one embodiment.

FIG. 7 is a flowchart of a method for controlling a controllable valveof an upper electrode assembly in accordance with at least oneembodiment.

DETAILED DESCRIPTION

It is understood that the following disclosure provides many differentembodiments, or examples, for implementing different features of thepresent application. Specific examples of components and arrangementsare described below to facilitate the illustrations presented in thepresent disclosure. These are, of course, examples and are not intendedto be limiting. For example, the formation of a first feature over or ona second feature in the description that follows may include embodimentsin which the first and second features are formed in direct contact, andmay also include embodiments in which additional features may be formedbetween the first and second features, such that the first and secondfeatures may not be in direct contact. In addition, the presentdisclosure may repeat reference numerals and/or letters in the variousexamples. This repetition is for the purpose of simplicity and clarityand does not in itself dictate a relationship between the variousembodiments and/or configurations discussed.

FIG. 1 is a cross-sectional view of a plasma treatment apparatus 100.Plasma treatment apparatus 100 includes a wafer treatment device 110having a vapor chamber 112. Wafer treatment device 110 also includes anupper electrode assembly 120 disposed at a top portion of wafertreatment device 110.

Upper electrode assembly 120 is configured to supply treatment gas intovapor chamber 112. Upper electrode assembly 120 includes a gasdistribution plate 122 having a plurality of holes 124. Upper electrodeassembly 120 further includes an upper electrode 126 having at least onegas nozzle 128 and at least one controllable valve 129. Each gas nozzle128 is connected to a corresponding controllable valve 129. In someembodiments, controllable valve 129 comprises a gate valve, a globevalve, a pinch valve, a diaphragm valve, a needle valve or anothersuitable valve. The at least one gas nozzle 128 is configured to conducttreatment gas to the plurality of holes 124.

Wafer treatment device 110 further includes a wafer support assembly 130disposed at a base portion of wafer treatment assembly 110. Wafersupport assembly 130 supports a wafer W inside vapor chamber 112 toexpose wafer W to treatment gas emitted from holes 124.

Wafer treatment device 110 further includes a gas supply 140 configuredto store a volume of treatment gas. Gas supply 140 is connected via agas inlet 142 to a gas chamber 144. Gas chamber 144 is connected to theat least one gas nozzle 128 to supply gas to vapor chamber 112.

Plasma treatment apparatus 100 further includes a controller 150configured to generate a control signal to cause adjustment ofcontrollable valves 129. Controller 150 is connected to wafer treatmentdevice 110 by a wired or wireless connection.

Controlling controllable valves 129 individually allows plasma treatmentapparatus 100 to control asymmetric flow of the treatment gas withinvapor chamber 112, which helps increase uniformity of an exposed surfaceof wafer W. Uniformity is determined based on gradients of variablessuch as thickness, critical dimension, layer composition, etc. If thegradient of a variable across the exposed surface of wafer W is small,the uniformity is high. Uniformity is increased by selective opening andclosing controllable valves 129 to more evenly distribute the treatmentgas within vapor chamber 112. As uniformity of the exposed surface ofwafer W increases, production yield also increases because more diesformed on the exposed surface pass quality control tests.

In some embodiments, a discharge direction of at least one gas nozzle128 is adjustable. In some embodiments, the discharge direction isadjustable in two dimensions parallel to a plane of a bottom surface ofupper electrode 126. In some embodiments, an actuator is connected toeach gas nozzle 128 to adjust the discharge direction of gas nozzle 128.In some embodiments, controller 150 is connected to the actuator tocontrol the discharge direction of at least one gas nozzle 128. In someembodiments, a separate controller, different from controller 150, isconnected to the actuator to control the discharge direction of the atleast one gas nozzle 128. Controlling the discharge direction of the atleast one gas nozzle 128 controls the distribution of treatment gaswithin vapor chamber 112, thereby facilitating asymmetric flow oftreatment gas.

In some embodiments, plasma treatment apparatus 100 is configured foretching a pattern into wafer W. In some embodiments, plasma treatmentapparatus 100 is configured for depositing a layer onto wafer W.Asymmetric flow of treatment gas within vapor chamber 112 increases theprecision of each process. Asymmetric flow of treatment gas in vaporchamber 112, increases uniformity of an amount of etching at eachlocation across the exposed surface of wafer W. Similarly, asymmetricflow of treatment gas in vapor chamber 112 results in a deposited layerhaving a uniform thickness across the exposed surface of wafer W. A highlevel of uniformity across the exposed surface of wafer W increases anumber of usable dies formed on wafer W. For example, in flip chipbonding processes, bonding pads or pillars having poor height or sizeuniformity often results in insufficient bonding and a failed device.

FIG. 2 is an exploded perspective view of upper electrode 120 inaccordance with some embodiments. Discharge ports 202 are in the bottomsurface of upper electrode 126. Discharge treatment gas is emitted intovapor chamber 112 through holes 124. In some embodiments, dischargeports 202 are aligned with holes 124. In some embodiments, dischargeports 202 are not aligned with holes 124.

In some embodiments, gas distribution plate 122 is bonded to a lowermajor surface of upper electrode 126. In some embodiments, bonding ofgas distribution plate 122 to upper electrode 126 is accomplished usinga silicone-based adhesive having different types of fillers tailored forenhancing thermal conductivity. In some embodiments, a gap remainsbetween gas distribution plate 122 and upper electrode 126 followingbonding. The gap helps to compensate for misalignment between dischargeports 202 and holes 124. The gap also facilitates changing the dischargedirection of at least one gas nozzle 128 by allowing the gas nozzle 128to direct flow toward specific holes 124.

FIG. 3 is a cross-sectional view of upper electrode assembly 120.Treatment gas from gas supply 140 enters upper electrode assembly 120through gas inlet 142. The treatment gas is dispersed in gas chamber144. Gas chamber 144 enables distribution of the treatment gas to eachgas nozzle 128 within upper electrode assembly 120. In operation,controllable valves 129 regulate flow of the treatment gas throughindividual gas nozzles 128. For example, by partially closingcontrollable valves 129 for gas nozzles 128 located near a centralportion 302 of upper electrode assembly 120, a larger volume oftreatment gas flows through peripherally located gas nozzles 128. Thus,by individually controlling gas flow through each gas nozzle 128, anasymmetric flow of treatment gas is produced within vapor chamber 112.

FIGS. 4A-D are bottom views of various gas distribution plates 122 forthe upper electrode assembly 120 in accordance with at least oneembodiment. In the embodiment of FIG. 4A, holes 124 are arranged in aregular lattice structure. Adjacent holes 124 across a bottom surface ofgas distribution plate are separated by a regular distance.

In the embodiment of FIG. 4B, holes 124 are arranged in a radialpattern. Holes 124 are spaced along lines extending from a center of gasdistribution plate 126 to an outer edge of the gas distribution plate. Aspacing between holes 124 of adjacent lines increases as a distance fromthe center of gas distribution plate 126 increases.

In the embodiment of FIG. 4C, holes 124 are arranged in an inner pattern402 and an outer pattern 404. Inner pattern 402 is a concentric patternhaving holes 124 arranged in concentric rings around the center of gasdistribution plate 126. Outer pattern 404 is a radial pattern with holesspaced along lines extending toward the center of gas distribution plate126.

In the embodiment of FIG. 4D, holes 124 are arranged in inner pattern402 and outer pattern 404. Inner pattern 402 is a concentric patternhaving holes 124 arranged in concentric rings around the center of gasdistribution plate 126. Outer pattern 404 is a radial pattern with holesspaced along lines extending toward the center of gas distribution plate126. In contrast with FIG. 4C, inner pattern 402 of FIG. 4D covers alarger surface area of gas distribution plate 126. Also, spacing betweenconcentric rings of inner pattern 402 is larger in FIG. 4D than in FIG.4C.

In some embodiments, gas distribution plate 126 has one pattern of holes124 across the bottom surface of the gas distribution plate. In someembodiments, gas distribution plate 126 has more than one pattern ofholes across the bottom surface of the gas distribution plate. In someembodiments, spacing between holes 124 on the bottom surface of gasdistribution plate 126 is irregular. In some embodiments, gasdistribution plate 126 has a different pattern of holes 124.

FIG. 5 is a block diagram of a feedback control system 500 in accordancewith at least one embodiment. Feedback control system 500 includes wafertreatment device 110, controller 150 and a measurement device 502.Measurement device 502 is configured to measure a thickness profile ofwafer W and transmit the thickness measurement to controller 150.Controller 150 is configured to receive the thickness measurement andgenerate a control signal based on the thickness measurement. Thecontrol signal is transmitted to wafer treatment device 110 to adjustcontrollable valves 129. In some embodiments, controller 150 generatesone control signal for each controllable valve 129. In some embodiments,controller 150 generates a number of control signals different than thenumber of controllable valves 129 and circuitry in wafer treatmentdevice 110 routes the control signals to controllable valves 129.

In operation, wafer treatment device 110 treats wafer W. In someembodiments, wafer W is subjected to an etching process. In someembodiments, a layer is deposited on wafer W. Following treatment ofwafer W, wafer W is transferred to measurement device 502.

The thickness profile of wafer W is measured using measurement device502. In some embodiments, measurement device 502 is a metrology tool. Insome embodiments, measurement device 502 uses Fourier transform infrared(FTIR) spectroscopy to measure wafer W. After the FTIR data is obtained,the thickness profile of wafer W is calculated using Beer's Law orSnell's Law. In some embodiments, measurement device 502 is a NOVA®3090, a KLA-TENCOR® FX100 or other suitable metrology tool.

After the thickness profile of wafer W is measured, the thicknessmeasurement is transmitted to controller 150. In some embodiments, thethickness measurement is transmitted using a wired connection. In someembodiments, the thickness measurement is transmitted using a wirelessconnection. Controller 150 is configured to receive the thicknessmeasurement and generate the control signal based on the thicknessmeasurement.

FIG. 6 is a schematic diagram of controller 150 in accordance with atleast one embodiment. Controller 150 includes an input/output (I/O)device 602 configured to receive/transmit signals from/to devicesexternal to controller 150. I/O device 602 is connected to a processor606 by a bus line 604. Processor 606 is configured to calculate valuesbased on information received from I/O device 602 and information storedin a memory 608. Memory 608 is connected to I/O device 602 and processor606 by bus line 604. Memory 608 includes a storage device 609.

Memory 608 comprises, in some embodiments, a random access memory (RAM)and/or other dynamic storage device and/or read only memory (ROM) and/orother static storage device, coupled to bus 604 for storing data andinstructions to be executed by processor 606. Memory 608 is also used,in some embodiments, for storing temporary variables or otherintermediate information during execution of instructions to be executedby processor 606.

Storage device 609, such as a magnetic disk or optical disk, isprovided, in some embodiments, and coupled to bus 604 for storing dataand/or instructions. I/O device 602 comprises an input device, an outputdevice and/or a combined input/output device for enabling userinteraction with controller 150. An input device comprises, for example,a keyboard, keypad, mouse, trackball, trackpad, and/or cursor directionkeys for communicating information and commands to the processor 606. Anoutput device comprises, for example, a display, a printer, a voicesynthesizer, etc. for communicating information to a user.

In some embodiments, the generation of the control signal is realized bya processor, e.g., processor 606, which is programmed for performingsuch processes. One or more of the memory 608, storage device 609, I/Odevice 602, and bus 604 is/are operable to receive design rules and/orother parameters for processing by processor 606. One or more of memory608, storage 609, I/O device 602, and bus 604 is/are operable to outputthe control signal as determined by processor 606.

In some embodiments, one or more of the processes is/are performed byspecifically configured hardware (e.g., by one or more applicationspecific integrated circuits or ASIC(s)) which is/are provided) separatefrom or in lieu of the processor. Some embodiments incorporate more thanone of the described processes in a single ASIC.

In some embodiments, the processes are realized as functions of aprogram stored in a non-transitory computer readable recording medium.Examples of a non-transitory computer readable recording medium include,but are not limited to, external/removable and/or internal/built-instorage or memory unit, e.g., one or more of an optical disk, such as aDVD, a magnetic disk, such as a hard disk, a semiconductor memory, suchas a ROM, a RAM, a memory card, and the like.

In some embodiments, storage device 609 is configured to store at leastone value related to the thickness measurement 610, a previous thicknessmeasurement 612 and a valve position 614. In some embodiments, storagedevice 609 stores a separate value for the valve position of eachcontrollable valve 129. In some embodiments, storage device 609 isconfigured to store values for different or additional variables.

Returning to FIG. 5 , controller 150 generates the control signal basedon the thickness measurement, the previous thickness measurement and thevalve position and transmits the control signal to wafer treatmentdevice 110. At least one controllable valve 129 of wafer treatmentdevice 110 are at least partially opened or closed based on the controlsignal. A second wafer is then treated using wafer treatment device 110.A thickness profile of the second wafer is measured and another controlsignal is generated based on the thickness measurement.

In some embodiments, the control signal is generated following treatmentof each wafer W. In some embodiments, by generating the control signalfollowing the polishing of each wafer W, the number of wafers W thatpass quality control testing for a given batch is increasable ascompared to less frequency generating of the control signal.

Further, a treatment environment of wafer treatment device 110 ischangeable over time due to factors such as deposits forming on walls ofvapor chamber 112, variations in treatment gas pressure orconcentration, or wear of the controllable valves 129.

In some embodiments, the control signal is generated based on apredefined number of wafers W treated since a previous generation of thecontrol signal, or after a predefined elapsed time. In some embodiments,the predefined number of wafer W ranges from about 10 to about 30. Insome embodiments, the predefined elapsed time ranges from about 2minutes to about 30 minutes. By generating the control signalperiodically, an overall processing speed is increasable as compared tomore frequent generation of the control signal.

FIG. 7 is a flowchart of a method 700 of controlling one controllablevalve 129 of an upper electrode assembly 120 in accordance with at leastone embodiment. In optional operation 702, controllable valve 129 is setto an initial position. In some embodiments, the initial position is adefault position. In some embodiments, the initial position is aposition set using the control signal from a previous wafer treatmentprocess. In some embodiments, controllable valve 129 is set to theinitial position using a setting signal from controller 150. In someembodiments, controllable valve 129 is set to the initial position basedon a user input.

In operation 704, a predetermined number of wafers are treated. Thewafers are treated using wafer treatment device 110. In someembodiments, the wafers are subjected to an etching process. In someembodiments, the wafers are subjected to a deposition process. In someembodiments, the predetermined number of wafers is one. In someembodiments, the predetermined number of wafers is more than one.

In operation 706, a thickness profile of at least one wafer is measured.The thickness profile is measured using measurement device 502. In someembodiments, the thickness profile of a single wafer is measured. Insome embodiments, the thickness profile for more than one wafer ismeasured. By measuring the thickness profile of the single wafer, theoverall processing speed is increased as compared to measuring thethickness profile for more than one wafer. By measuring the thicknessprofile for more than one wafer, a more accurate control signal isgenerated as compared to measuring the thickness profile of the singlewafer.

In operation 708, the thickness profile is compared to the previousthickness profile. The previous thickness profile is stored incontroller 150. The comparison is performed by the controller 150.

In operation 710, a control signal is generated based on the comparisonresults. Controller 150 generates the control signal based on thecomparison results and transmits the control signal to wafer treatmentdevice 110.

In operation 712, controllable valve 129 is adjusted based on thecontrol signal. Circuitry within wafer treatment device 110 routes thecontrol signal to controllable valve 129 to adjust controllable valve129. In some embodiments, controllable valves 129 are controlled usingmotors, piezoelectric actuators or other suitable actuators.

An aspect of this description relates to a control system for a plasmatreatment apparatus. The control system includes a wafer treatmentdevice. The wafer treatment device includes a vapor chamber and an upperelectrode assembly. The upper electrode assembly includes a gasdistribution plate having a plurality of holes in a bottom surfacethereof. The upper electrode assembly further includes an upperelectrode having at least one gas nozzle and at least one controllablevalve connected to the at least one gas nozzle for controlling a flow ofgas from a gas supply to the holes via the at least one gas nozzle. Theat least one gas nozzle is separated from the gate distribution plate bya gap. The control system further includes a measurement deviceconfigured to measure a thickness profile of a wafer. The control systemfurther includes a controller configured to generate a control signal.The at least one controllable valve is configured to be adjusted basedon the control signal. In some embodiments, the measurement device isconfigured to transmit the measured thickness profile to the controller.In some embodiments, the controller is configured to generate thecontrol signal based on the measured thickness profile. In someembodiments, the plurality of holes is arranged in at least one patternacross the bottom surface of the gas distribution plate. In someembodiments, the plurality of holes is arranged in a first patternproximate a center of the bottom surface of the gas distribution plateand a second pattern surrounding the first pattern, and the firstpattern and the second pattern are different.

An aspect of this description relates to a control system for a plasmatreatment apparatus. The control system includes an electrode assembly.The electrode assembly includes a gas distribution plate having aplurality of holes in a surface thereof. The electrode assembly furtherincludes an electrode having a gas nozzle and a controllable valveconnected to the gas nozzle for controlling a flow of gas to theplurality of holes via the gas nozzle, wherein the gas nozzle isseparated from the gas distribution plate by a gap. The control systemfurther includes a controller configured to generate a control signal,wherein the controllable valve is configured to be adjusted based on thecontrol signal. In some embodiments, the controller is configured togenerate the control signal based on a measured thickness profile of awafer. In some embodiments, the controller is configured to generate thecontrol signal based on a comparison between the measured thicknessprofile and a previous thickness profile. In some embodiments, the gasdistribution plate includes an inner region and an outer region, theouter region surrounds the inner region, holes of the plurality of holesin the inner region are in a first pattern, and holes of the pluralityof holes in the outer region are in a second pattern. In someembodiments, the controller is configured to generate an initialposition signal prior to treatment of a wafer, and the controllablevalve is configured to be adjusted based on the initial position signal.In some embodiments, the controller is configured to generate theinitial position signal based on a thickness profile of a previouslyprocessed wafer. In some embodiments, the upper electrode assemblyfurther includes a second controllable valve. In some embodiments, thesecond controllable valve is configured to be adjusted based on thecontrol signal. An aspect of this description relates to a controlsystem for a plasma treatment apparatus. The control system includes anelectrode assembly. The electrode assembly includes a gas distributionplate. The gas distribution plate includes an inner region having afirst plurality of holes arranged in a first pattern, and an outerregion surrounding the inner region, wherein the outer region has asecond plurality of holes arranged in a second pattern. The electrodeassembly further includes an electrode having a gas nozzle and aplurality of controllable valves connected to the gas nozzle forcontrolling a flow of gas to the plurality of holes via the gas nozzle,wherein the gas nozzle is separated from the gas distribution plate by agap. The control system further includes a controller configured togenerate a control signal, wherein each of the plurality of controllablevalves is configured to be adjusted based on the control signal. In someembodiments, a first controllable valve of the plurality of controllablevalves is configured to open in response to the control signal, and asecond controllable valve of the plurality of controllable valves isconfigured to close in response to the control signal. In someembodiments, the plurality of controllable valves is configured togenerate an asymmetric flow of the gas based on the control signal. Insome embodiments, the controller is configured to generate the controlsignal based on a measured thickness profile of a wafer. In someembodiments, the first pattern is different from the second pattern. Insome embodiments, a discharge direction of the gas nozzle iscontrollable based on a second control signal from the controller, andthe second control signal is different from the control signal. In someembodiments, a discharge direction of the gas nozzle is controllablebased on the control signal.

It will be readily seen by one of ordinary skill in the art that thedisclosed embodiments fulfill one or more of the advantages set forthabove. After reading the foregoing specification, one of ordinary skillwill be able to affect various changes, substitutions of equivalents andvarious other embodiments as broadly disclosed herein. It is thereforeintended that the protection granted hereon be limited only by thedefinition contained in the appended claims and equivalents thereof.

What is claimed is:
 1. A control system for a plasma treatment apparatuscomprising: a wafer treatment device comprising: a vapor chamber; and anupper electrode assembly comprising: a gas distribution plate, whereinthe gas distribution plate comprises: an inner region having a firstplurality of holes arranged in a first pattern, and an outer regionsurrounding the inner region, wherein the outer region has a secondplurality of holes arranged in a second pattern; and an upper electrodehaving at least one gas nozzle and at least one controllable valveconnected to the at least one gas nozzle for controlling a flow of gasfrom a gas supply to the holes via the at least one gas nozzle, whereinthe at least one gas nozzle is separated from the gas distribution plateby a gap; a measurement device configured to measure a thickness profileof a wafer; and a controller configured to generate a control signal,wherein the at least one controllable valve is configured to be adjustedbased on the control signal.
 2. The control system of claim 1, whereinthe measurement device is configured to transmit the measured thicknessprofile to the controller.
 3. The control system of claim 2, wherein thecontroller is configured to generate the control signal based on themeasured thickness profile.
 4. The control system of claim 1, whereinthe at least one controllable valve comprises a plurality ofcontrollable valves.
 5. The control system of claim 1, wherein the firstpattern is proximate a center of the bottom surface of the gasdistribution plate.
 6. A control system for a plasma treatment apparatuscomprising: an electrode assembly comprising: a gas distribution platehaving a plurality of holes in a surface thereof; and an electrodehaving a gas nozzle and a controllable valve connected to the gas nozzlefor controlling a flow of gas to the plurality of holes via the gasnozzle, wherein the gas nozzle is separated from the gas distributionplate by a gap; and a controller configured to generate a controlsignal, wherein the controllable valve is configured to be adjustedbased on the control signal.
 7. The control system of claim 6, whereinthe controller is configured to generate the control signal based on ameasured thickness profile of a wafer.
 8. The control system of claim 7,wherein the controller is configured to generate the control signalbased on a comparison between the measured thickness profile and aprevious thickness profile.
 9. The control system of claim 6, whereinthe gas distribution plate comprises an inner region and an outerregion, the outer region surrounds the inner region, holes of theplurality of holes in the inner region are in a first pattern, and holesof the plurality of holes in the outer region are in a second pattern.10. The control system of claim 6, wherein the controller is configuredto generate an initial position signal prior to treatment of a wafer,and the controllable valve is configured to be adjusted based on theinitial position signal.
 11. The control system of claim 10, wherein thecontroller is configured to generate the initial position signal basedon a thickness profile of a previously processed wafer.
 12. The controlsystem of claim 6, wherein the electrode assembly further comprises asecond controllable valve.
 13. The control system of claim 12, whereinthe second controllable valve is configured to be adjusted based on thecontrol signal.
 14. A control system for a plasma treatment apparatuscomprising: an electrode assembly comprising: a gas distribution plate,wherein the gas distribution plate comprises: an inner region having afirst plurality of holes arranged in a first pattern, and an outerregion surrounding the inner region, wherein the outer region has asecond plurality of holes arranged in a second pattern; and an electrodehaving a gas nozzle and a plurality of controllable valves connected tothe gas nozzle for controlling a flow of gas to the plurality of holesvia the gas nozzle, wherein the gas nozzle is separated from the gasdistribution plate by a gap; and a controller configured to generate acontrol signal, wherein each of the plurality of controllable valves isconfigured to be adjusted based on the control signal.
 15. The controlsystem of claim 14, wherein a first controllable valve of the pluralityof controllable valves is configured to open in response to the controlsignal, and a second controllable valve of the plurality of controllablevalves is configured to close in response to the control signal.
 16. Thecontrol system of claim 14, wherein the plurality of controllable valvesis configured to generate an asymmetric flow of the gas based on thecontrol signal.
 17. The control system of claim 14, wherein thecontroller is configured to generate the control signal based on ameasured thickness profile of a wafer.
 18. The control system of claim14, wherein the first pattern is different from the second pattern. 19.The control system of claim 14, wherein a discharge direction of the gasnozzle is controllable based on a second control signal from thecontroller, and the second control signal is different from the controlsignal.
 20. The control system of claim 14, wherein a dischargedirection of the gas nozzle is controllable based on the control signal.